PLANT HEALTH CARE TH CARE
DUTCH ELM DISEASE: Then and Now
By Br andon Gallagher Watson I
t can probably be claimed, with little objection of hypebole, that introduction of Dutch elm disease (DED) to Europe and North America is the most significant event in the history of urban forestry. Sounds lofty to say, but think about it; it affected everything from
the way we view monoculture street plantings to our understanding of invasive pests. It forever altered urban forestry policy and law, and certainly changed the public's awareness of street tree management. Arborists trying to combat the devastation of this disease pioneered the profession of "tree health care,
" opening up an entirely new industry
for managing the care of urban trees. Even our current emerald ash borer pandemic is directly linked to Dutch elm disease,as the majority of today's ash trees are replacements for lost elms. As the impact of Dutch elm disease is linked to history of urban
forestry, its introduction to America is intricately linked to the history of America,and in a way, the American Dream itself.World War I ended and American soldiers returning were in need of housing.This caused a demand for timber required for the homes themselves and the furnish- ings that would go inside them.American manufacturers began sourcing
18 Arbor Age / May/June 2012
wood from other countries,including those in Europe. Meanwhile, in Europe, elm trees had been inexplicably dying for nearly 20 years.The timing of the deaths around The Great War and the way a seemingly healthy tree would up and die in midsummer led many to assume the deaths were related to nerve gas used by combatants.A young phytopathologist from the Netherlands named Bea Schwartz first isolated a fungus from the dying elms in 1921,which would give rise to the Dutch elm disease moniker. Later it was discovered the fungus originated in Asia where elms had evolved a resistance to the fungus over several millions of years.The elms in Europe had no defense,and thus were dying by the millions after it arrived.Brittan alone lost more than 25 million elms in a just a 30-year span. Back in America,elms were being planted along pretty much every
boulevard they could be planted along.Their durable nature,rapid growth, and the pleasing vase-shape of the mature trees made them a seemingly perfect street tree.Many cities had hundreds of thousands of boulevard elms; in fact, to this day, Elm Street is the fifteenth most popular street name in the United States.The house, the yard, the picket fence, and
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